CMake Windows warning CMP0115

[emersonknapp]

This is making the ROS2 buildfarm go yellow on the nightlies - see for example https://ci.ros2.org/view/nightly/job/nightly_win_deb/1943/consoleText

The warning output is as follows

CMake Warning (dev) at src/idl/CMakeLists.txt:41 (add_library):
  Policy CMP0115 is not set: Source file extensions must be explicit.  Run
  "cmake --help-policy CMP0115" for policy details.  Use the cmake_policy
  command to set the policy and suppress this warning.

  File:

    C:/ci/ws/src/eclipse-cyclonedds/cyclonedds/src/idl/src/hashid.c.in
This warning is for project developers.  Use -Wno-dev to suppress it.

[eboasson]

@k0ekk0ek just from the name of the file involved I think this relates to #735. Are you ok with me leaving it for you to look into in more detail?

[k0ekk0ek]

@eboasson, absolutely, but I missed the notification. I'll have a go at it.

[k0ekk0ek]

I think this particular issue is fixed by #737. Looking at the description provided in #756, I think CMake previously searched for hashid.c and found hashid.c.in. The error of course being it should use the generated version. I've tried to reproduce locally with CMake 3.20, but the warning didn't occur. The warning also isn't in the latest ROS builds, so I think we can safely close this. @emersonknapp, do you agree?

[emersonknapp]

Yep, this was opened to make ROS builds green - I don't have any particular input beyond that :)

[k0ekk0ek]

Closing this issue. Thanks for the feedback.